The invention relates to medical articles that include substrates having a diamond-like carbon coating. More particularly, the invention relates to medical articles including a polymer material with a diamond-like carbon coating.
A variety of medical articles are designed particularly for contact with a patient""s bodily fluids. The duration of this contact may be relatively short, as is typical with wound dressings, burn dressings and contact lenses, or may be long term, as is typical with implanted prostheses, such as prosthetic heart valves implanted into the body of a recipient. Some articles, such as catheters, can have either short term or relatively long term contact.
Prostheses, i.e., prosthetic articles, are used to repair or replace damaged or diseased organs, tissues and other structures in humans and animals. Prostheses generally must be biocompatible since they are typically implanted for extended periods of time. Physicians use a variety of prostheses to correct problems associated with the cardiovascular system, especially the heart. For example, the ability to replace or repair diseased heart valves with prosthetic devices has provided surgeons with a method of treating heart valve deficiencies due to disease and congenital defects. A typical procedure involves removal of the native valve and surgical replacement with a mechanical or bioprosthetic, i.e., tissue based, valve. Another technique uses an annuloplasty ring to provide structural support to the natural annulus of the native valve.
Many biocompatible medical devices and/or their components have important requirements with respect to their mechanical and physical properties. For example, the medical devices are often limited in their size. At the same time, the devices and/or their components may be subjected to demanding structural requirements, such as mechanical strength and long term wear requirements. Thus, there are significant restraints imposed on the design of many medical devices and/or their components.
As a particular example, prosthetic heart valve leaflets or occluders perform the function of opening and closing to regulate the blood flow through the heart valve. Typically, heart valve leaflets must either pivot or flex with each cycle of the heart to open and close. Leaflets in purely mechanical heart valve prostheses generally pivot to open and close the valve. In bioprostheses, flexible leaflets are designed to approximate natural leaflet function. While these leaflets are flexible, they must have a well defined and stable configuration to properly close the valve at each cycle to reduce back flow. Also, the leaflets should be durable to provide stable performance over many years of use.
Conventional bioprostheses use tissue that has been appropriately processed. For example, a natural allograft or xenograft heart valve can be processed to produce a heart valve prosthesis. While tissue leaflets have desired flexibility and acceptable hemodynamic performance, tissue leaflets can calcify after implantation, which results in loss of flexibility resulting in improper closure or opening of the valve.
In a first aspect, the invention pertains to a medical article suitable for contact with a patient""s blood, the medical article comprising a polymer substrate at least a portion of which is coated with a diamond-like carbon coating, the medical article being an implantable vascular device or an implantable cardiovascular device.
In a further aspect, the invention pertains to a method of making a medical article including applying a diamond-like carbon coating onto a polymer substrate and forming at least a portion of a medical article from the diamond-like carbon coated polymer substrate. The diamond-like carbon coating is preferably applied using ion beam assisted deposition. In some embodiments, the polymer substrate degrades at a temperature no more than about 200xc2x0 C., and in particular embodiments less than about 150xc2x0 C., and the application is performed under conditions at which the polymer substrate is not significantly structurally or chemically degraded.
In another aspect, the invention pertains to a heart valve prosthesis comprising at least one leaflet that is located along the flow path through the valve, in which the at least one leaflet can move to alter the amount of flow through the valve, the leaflet comprising a polymer substrate at least partially coated with diamond-like carbon.
In an additional aspect, the invention pertains to a medical article suitable for contact with a patient""s bodily fluids, the medical article comprising a polymer substrate, for example in selected flexible embodiments, at least a portion of which is coated with a diamond-like carbon coating, the polymer substrate having a thickness less than about 600 microns.